Methods and apparatus to implement current limit test mode

ABSTRACT

Methods, apparatus, systems and articles of manufacture are disclosed. An example apparatus includes a gate controller coupled between an input terminal and an intermediate node, the gate controller including a first transistor coupled between the input terminal and a first node; a second transistor coupled between the first node and the intermediate node; a third transistor coupled between the input terminal and the intermediate node; and a charge pump coupled to the intermediate node; a switching network coupled between the intermediate node and an output terminal, the switching network including a high-side drive (HSD) transistor having a HSD gate terminal coupled to the intermediate node, the HSD transistor coupled between an input voltage and a switch node.

RELATED APPLICATION

This patent is a continuation of U.S. patent application Ser. No.16/670,720 filed Oct. 31, 2019, which claims benefit of U.S. ProvisionalPatent Application Ser. No. 62/775,668, filed on Dec. 5, 2018, whichApplications are hereby incorporated herein by reference in theirentirety.

FIELD OF THE DISCLOSURE

This disclosure relates generally to current limiting, and, moreparticularly, to implementing current limit test mode.

BACKGROUND

Power converter circuits are used in various devices to convert inputvoltages to desired output voltages. For example, a buck converterconverts an input voltage into a lower, desired output voltage bycontrolling transistors and/or switches to charge and/or dischargeinductors and/or capacitors to maintain the desired output voltage. Suchtransistors/switches conduct current and, like most devices, have athreshold of current they are able to conduct until thetransistor/switch is damaged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an example voltage converterapparatus which operates in three modes.

FIG. 2 is a schematic illustration depicting additional detail of theexample voltage converter apparatus of FIG. 1 .

FIG. 3 is signal plot illustrating a transient response of the elementsof the example voltage converter apparatus of FIG. 2 when operating in afirst mode.

FIG. 4 is a signal plot illustrating a transient response of theelements of the example voltage converter apparatus of FIG. 2 whenoperating in a second mode.

FIG. 5 depicts schematic illustrations of a test mode implementationcircuit and an example gate controller of the example voltage converterapparatus of FIG. 2 .

FIG. 6 depicts a schematic layout of an example gate driver includingthe example gate controller.

FIG. 7 depicts a flowchart representative of machine readableinstructions which may be executed to implement the example gatecontroller of FIG. 2 to enable the first mode, the second mode, and athird mode of operation.

The figures are not to scale. In general, the same reference numberswill be used throughout the drawing(s) and accompanying writtendescription to refer to the same or like parts. As used in this patent,stating that any part (e.g., a layer, film, area, region, or plate) isin any way on (e.g., positioned on, located on, disposed on, or formedon, etc.) another part, indicates that the referenced part is either incontact with the other part, or that the referenced part is above theother part with one or more intermediate part(s) located therebetween.Stating that any part is in contact with another part means that thereis no intermediate part between the two parts. Although the figures showlayers and regions with clean lines and boundaries, some or all of theselines and/or boundaries may be idealized. In reality, the boundariesand/or lines may be unobservable, blended, and/or irregular.

Descriptors “first,” “second,” “third,” etc. are used herein whenidentifying multiple elements or components which may be referred toseparately. Unless otherwise specified or understood based on theircontext of use, such descriptors are not intended to impute any meaningof priority or ordering in time but merely as labels for referring tomultiple elements or components separately for ease of understanding thedisclosed examples. In some examples, the descriptor “first” may be usedto refer to an element in the detailed description, while the sameelement may be referred to in a claim with a different descriptor suchas “second” or “third.” In such instances, it should be understood thatsuch descriptors are used merely for ease of referencing multipleelements or components.

DETAILED DESCRIPTION

As used herein, the term “above” is used with reference to a bulk regionof a base semiconductor substrate (e.g., a semiconductor wafer) on whichcomponents of an integrated circuit are formed. Specifically, as usedherein, a first component of an integrated circuit is “above” a secondcomponent when the first component is farther away from the bulk regionof the semiconductor substrate. Likewise, as used herein, a firstcomponent is “below” another component when the first component iscloser to the bulk region of the semiconductor substrate. As notedabove, one component can be above or below another with other componentstherebetween or while being in direct contact with one another.

Switched mode power converters (e.g., boost converters, buck converters,buck-boost converters, etc.), or power conversion stages, are used toconvert a first voltage (e.g., an input voltage) to a second voltage(e.g., an output voltage). Such power converters include a switchingnetwork including one or more switching transistors coupled to aswitching node that is switched to form circuit arrangements to directcurrent through an energy storage inductor and/or to charge/discharge anoutput capacitor. Such circuit arrangements supply load current andregulate the output voltage to remain substantially steady at the secondvoltage.

In some examples, a buck converter includes two main power transistors.A power transistor, such as a metal-oxide semiconductor field-effecttransistor (MOSFET), includes two current terminals and a gate terminal.To turn on the MOSFET (e.g., initiate current conducting through the twocurrent terminals), a voltage is applied to the gate terminal, and theamount of voltage determines the amount of current the MOSFET willconduct. The two main power transistors can conduct an excessive amountof current during a circuit over current (e.g., excess current existingthrough a conductor leading to excessive generation of heat), atransient (e.g., a large spike of current generated by a load or thestart-up of a voltage supply), or a short circuit (e.g., an unintendedcontact of electrical components such as a voltage directly coupled toground, resulting in low impedance and high current). When such powertransistors conduct excessive amounts of current, they generate heat,sometimes too much heat, and become damaged and therefore stop workingas intended. In order to protect such power transistors from conductingexcessive current, a current limit is implemented.

A current limit can be implemented by a current limiting circuit. Acurrent limiting circuit is utilized to impose an upper limit on thecurrent that is delivered to the load to protect the power converter,that is transmitting the current, from harmful effects. In someexamples, a current limiting circuit turns off (e.g., switches off,removes power, etc.) the power transistor when it senses the currentconducting through the transistor has exceeded the upper limit ofcurrent. In order to determine if the current limiting circuit issensing the current conducting through the power transistors andswitching off the power transistors when the current exceeds the upperlimit, a manufacturer must test the current limiting circuit.

In some examples, the current limiting mechanisms are tested in anautomated test environment (ATE). ATE can also be defined as automatictest equipment. ATE includes control hardware, sensors, and softwarethat performs tests on the current limiting circuit and further collectsand analyzes the test results. Some examples of ATE resources (e.g.,test hardware, sensors, analog inputs and outputs, digital inputs andoutputs, and software) include a computer, a digital signal processor(DSP) for analog testing, a test program/software operating on thecomputer, a probe head that touches a probe pad, a probe card ormembrane probe to measure signal on a pin or pad of the circuit, etc.The ATE resources may have limited current capabilities. For example,the test hardware such as the current sources or current sinks, whichare used for testing, can only provide milliamps of current.

In some examples, a power converter such as a buck converter, has anupper limit of current in the ampere range. For example, a powertransistor of the power converter may conduct eight amperes of current,which is greater than milliamps of current. Therefore, it isdifficult/not possible to test a current limiting circuit with ATEsystems due to the ATE hardware having limited current capabilities.Further, manufacturers, designers, engineers, etc., design a scaled downversion of a switching network in order for the ATE resources toproperly test the current limiting circuit. For this purpose, it has tobe rendered possible to turn on only a portion of the power transistorto test the current limiting circuit. In some examples, it is trivial toturn on only a portion of power transistors such as a low-side N-ChannelMOSFET and a high-side P-Channel MOSFET. In examples disclosed herein,it is not trivial to turn on a portion of a the high-side N-ChannelMOSFET.

To turn on only a portion of the power transistor to test the currentlimiting circuit, the power transistor of the power converter is splitinto two transistors, where the two transistors are coupled in parallelto each other. For example, one transistor may be 90 percent of the sizeof the original transistor and a second transistor may be 10 percent ofthe size of the original power transistor. In this manner, the ATEhardware can test the operation of the current limiting circuit byturning on only the smaller transistor which increases the impedance ofthe parallel connection of the two transistors. For example, bysplitting the power transistor into two transistors, where one is largeand the other is small, a ratio is created. The ratio corresponds to theratio of the maximum allowed current that will conduct during a normaloperation to the current the ATE resource is able to sink during a testmode operation.

For example, if the maximum allowed current is 10 amps during normaloperation and the ATE resource can only sink 100 milliamps duringcurrent limit test mode operation, then the ratio is 100. In thismanner, the smaller transistor is 1/100 the size of the originaltransistor and the bigger transistor is 99/100 the size of the originaltransistor. In this manner, the impedance of the small transistor isone-hundred times the impedance of the combination of the biggertransistor and the smaller transistor. Since the current limitingcircuitry senses the voltage drop across the transistors, the currentlimiting circuitry will trip at 100 milliamps of load current if onlythe small portion is on (e.g., because the voltage drop across the smalltransistor at 100 milliamps is the same as the voltage drop across theparallel connection of big and small transistor at 10 amps). A gatecontroller operates to turn on only the small transistor when thecurrent limiting circuit is being tested by the ATE resource.

Challenges may arise when designing a gate controller that is able toturn on both transistors when the power converter is in normal operationor one hundred percent mode operation and turn on only the smalltransistor and turn off the larger transistor when the power converteris being tested by an ATE system. Normal operation of the powerconverter includes turning on a high-side power transistor and turningoff a low-side power transistor and turning on the low-side powertransistor and turning off the high-side power transistor to provide aregulated output voltage to a load. one hundred percent mode operationis when the high-side power transistor is on one hundred percent of thetime, and the voltage at the input of the power converter is provided tothe output. Challenges arise due to the requirement that in normal orone hundred percent mode operation, the gate terminals of the twotransistors (e.g., the big transistor and the small transistor) shouldhave the same voltage potential in order for the current limitingcircuit to work as intended, but in test mode operation, the gateterminals of the two transistors should not have the same voltagepotential and the bigger transistor should be off while the smallertransistor should be on.

Examples disclosed herein include a gate controller that controls theconnection between the two gate terminals of the transistors to achievenormal operation mode, one hundred percent operation mode, and test modewhen required. For example, the gate controller includes a P-channeltransistors (e.g., P-channel metal oxide semiconductor field-effecttransistors (MOSFET) (PMOS)) based switch to control the connectionbetween the two gate terminals of the bigger transistor and the smallertransistor. Examples disclosed herein also utilize one charge pump toassist the power converter to operate in one hundred percent mode.Additionally, the charge pump operates to turn on the small transistorduring current limit test mode. A charge pump is similar to a switchingregulator that delivers power to an output by only charging anddischarging capacitors.

In some examples, multiple charge pumps are utilized in the gatecontroller to turn on power transistors, which can take up a largesilicon area on a die (e.g., a small block of semi-conducting materialon which a given functional circuit is fabricated). Also in someexamples, two gate drivers are utilized to drive the gate terminals ofthe two transistors which takes up silicon area. The larger the area ofthe die, the more costly. Thus, examples disclosed herein decrease thearea size of power converter and gate driver schematic by utilizing onecharge pump, one gate driver, and the PMOS based switch of the gatecontroller.

FIG. 1 is a block diagram of an example voltage converter apparatus 100.The example voltage converter 100 includes an example switching network102 coupled to an example gate driver 104. The example gate driver 104includes an example first transistor 106 and an example secondtransistor 108, an example gate controller 110, and an exampleboot-strap capacitor (Cboot) 112 to boost (e.g., increase) a biasvoltage to provide a current to a drain terminal of the example firsttransistor 106.

In FIG. 1 , the example voltage converter apparatus 100 includes theexample switching network 102 to step down an input voltage to aregulated output voltage to power a load. The example switching network102 includes a plurality of power transistors to conduct current to flowinto the switching network 102 to the load via an output 116 or blockcurrent from flowing to the load via the output 116. The exampleswitching network 102 is coupled to receive a controlled voltage via theexample first transistor 106, an input voltage 118, and a controlledvoltage at node 126 via the example gate controller 110. The exampleswitching network 102 operates in three main modes: normal mode, onehundred percent mode, and current limit test mode. When the exampleswitching network 102 is operating in normal mode, the voltage on theswitching node 124 is a square wave, similar to a pulse-width modulation(PWM) signal. When the example switching network 102 is operating in onehundred percent mode, the voltage on the output 116 is equal to theinput voltage 118. When the example switching network 102 is operatingin current limit test mode, the voltage at switching node 124 and output116 are similar to the output during one hundred percent mode (e.g., thevoltage at the SW node 124 is the input voltage 118 minus a voltage dropacross the one or more high side drive transistors of the switchingnetwork 102).

In FIG. 1 , the example voltage converter 100 includes the example gatedriver 104 to receive an input signal (e.g., a PWM signal) from acontroller integrated-circuit and a switchable bias voltage circuit 103produce an amplified signal from the low-power input to inject into thegate terminals of the example MN0 106 and the example MN2 108. Forexample, the low-power input may be generated from a PWM generator. Insome examples, the PWM signal is a control signal that controls thecurrent conducting through the power transistors of the switchingnetwork 102. The PWM signal is a turn-on and/or turn-off signalgenerated to control the operation of the power transistors. A PWMsignal is injected into the example gate driver 104 to be amplified andinjected into the gate terminal of a switching transistor. The PWMsignal is an oscillating signal varying in duty cycle. Alternatively,the PWM signal may vary in frequency, therefore noted as a PulseFrequency Modulated signal (PFM).

The PWM and/or PFM signal injected into the gate driver 104 containsinformation pertaining to the turn on and/or turn off times of thetransistor. For example, the gate driver 104 may be configured toprovide a plurality of PWM signals to the transistors, wherein each PWMsignal may be the same and turn on transistors simultaneously, or theymay be different and turn on and off transistors in different timeintervals. In other examples, the PWM and/or PFM signal injected intothe gate terminal may contain information pertaining to the turn onand/or turn off times of any power switch.

In FIG. 1 , the example voltage converter apparatus 100 includes theexample gate driver 105 to receive a control signal (e.g., a PWM signal,PFM signal, etc.) from a controller and produce an amplified signal fromthe low-power input to inject into the gate terminals to control anoperation of a portion of the switching network 102. For example, thegate driver 105 controls the operation of a low-side drive (LSD)transistor of the switching network 102. The example gate driver 105 maybe a power amplifier on an integrated chip (IC) or on a discrete module.In other examples, the gate driver 105 may include a plurality ofelectrical components that work together to amplify a low-power inputsignal to turn on or turn off a LSD transistor of the switching network102.

In FIG. 1 , the example gate driver 104 includes the example firsttransistor 106 and the example second transistor 108. The example firsttransistor (MN0) 106 and the example second transistor (MN2) 108 areN-channel MOSFETs (NMOS). Alternatively, MN0 106 and MN2 108 may beP-Channel MOSFETs, PNP BJTs, NPN BJTs, etc. Alternatively, MN0 106 andMN2 108 may be a switch or any other type of power switching device.

An NMOS includes two current terminals and a gate terminal, wherein oneof the current terminals is a drain terminal and the second currentterminal is a source terminal. The gate terminal of an NMOS controls thecurrent that conducts out of the drain terminal to the source terminal.The NMOS operates in a linear mode when the gate-to-source voltage (Vgs)is greater than a threshold voltage (Vth) of the MOSFET and when thedrain-to-source voltage (Vds) is less than the Vgs minus the thresholdvoltage (e.g., Vgs>Vth; Vds<Vgs−Vth). When the NMOS is in triode mode,the current conducting through the drain terminal (Id) to the sourceterminal is dependent upon the amount of voltage applied to the gateterminal. For example, if Vgs is small, then little drain currentconducts, but when Vgs is big, then more drain current conducts. TheNMOS operates in a saturation mode when Vgs>Vth and when the voltage Vdsis greater than the voltage Vgs minus the threshold voltage (e.g.,Vgs>Vth; Vds>Vgs−Vth). When the NMOS is in saturation mode, the drainterminal and source terminal act like a current source. In linear mode,current conducting through the two terminals varies depending on anincreasing Vds voltage once the voltage has exceeded the threshold forsaturation. In saturation, the current varies depending on an increasinggate voltage. Lastly, the NMOS operates in a cut-off mode when the Vgsis less than the threshold voltage Vth. In cut-off mode, no draincurrent Id conducts through the terminals.

In the illustrated example, a drain terminal of the first transistor 106is coupled to the example Cboot 112, a gate terminal of the examplefirst transistor 106 is coupled to receive a first PWM signal (PWM), anda source terminal of the example first transistor 106 is coupled to adrain terminal of the example second transistor 108 at an exampleGATE_BIG node 122. In the illustrated example, a gate terminal of theexample second transistor 108 is coupled to receive a second PWM signal(PWM2), and a source terminal of the second transistor 108 is coupled toa portion of the switching network 102 at a switch (SW) node 124.

In FIG. 1 , the example gate driver 104 includes an example switchablebias voltage circuit 111 coupled to the example Cboot 112. Theswitchable bias voltage circuit 111 is a bias voltage supply thatprovides a voltage to the Cboot 112 depending on the PWM input at thePWM node 132 to the example gate driver 104. For example, a controller(e.g., a PWM generator) provides a high voltage signal to the gatedriver 104 which initiates the switchable bias voltage circuit 111 toprovide a voltage to the Cboot 112. In other examples, a controllerprovides a low-voltage signal to the gate driver 104 to cause theswitchable bias voltage circuit 111 to short the Cboot 112 to ground,thereby removing the voltage provided to the bottom plate of the Cboot112. The switchable bias voltage circuit 111 outputs a voltage that iscorresponding to the value of the incoming PWM signal that is providedto the example gate driver 104. For example, if the incoming PWM signalis low, the switchable bias voltage circuit 111 grounds the bottom plateof Cboot 112. If the incoming PWM signal is a high (e.g., 1 volt), theswitchable bias voltage circuit 111 applies a voltage to the bottomplate of the Cboot 112, thereby increasing the voltage at the boot strapnode 120. The switchable bias voltage circuit 111 is initiated (e.g.,outputs a high voltage) when the example voltage converter 100 isoperating in normal mode or one hundred percent mode and the switchablebias voltage circuit 111 does not output a high voltage to the exampleCboot 112 when the voltage converter 100 is operating in current limittest mode.

In FIG. 1 , the example gate driver 104 includes the example gatecontroller 110 to enable the ATE test of the circuitry, which imposes anupper limit of current on the example switching network 102. Forexample, the gate controller 110 includes a plurality of transistors,which may work together to adjust the impedance of a transistor ofcircuitry depending on the mode of operation. Essentially, the examplegate controller 110 controls the state of operation of the exampleswitching network 102 because the gate controller 110 decides which gateterminals of the switching network 102 to pull up (e.g., increase thevoltage to the output of the first transistor 106 or increase thevoltage to the voltage at node 126). The example gate controller 110 iscoupled to receive the input voltage 118 and determined to be coupled toreceive the controlled voltage from the example first transistor 106 orthe boosted voltage from the example Cboot 112.

In some examples, the gate controller 110 is to assist an ATE system intesting circuitry which imposes an upper limit of current on theswitching network 102 for proper operation during current limiting. Forexample, an ATE system with limited current capabilities may be used totest the circuitry, therefore the gate controller 110 must be able tocontrol a portion of the switching network 102, wherein the portion ofthe switching network will conduct a smaller amount of current than thewhole switching network 102 would conduct. In order to be able tocontrol (e.g., turn on and turn off) the whole switching network 102 ora portion of the switching network 102, the example gate controller 110is to be coupled to receive either the boosted voltage or the controlledvoltage. The example switching network 102 and the example gatecontroller 110 are described in further detail below in connection withFIG. 2 .

In FIG. 1 , the example gate driver 104 includes the example Cboot 112to boost or increase a bias voltage. A capacitor is a two terminalelectrical component which stores potential energy in an electric field.The example Cboot 112 includes a first capacitor terminal and a secondcapacitor terminal, the first capacitor terminal is coupled to aswitchable bias voltage circuit 111 of the example gate driver 104 andthe second capacitor terminal is coupled to the drain terminal ofexample MN0 106. A boot-strap capacitor acts to exceed the voltageoutput by the switchable bias voltage circuit 111 to twice the supplyvoltage (e.g., VIN 118) in order to enable the turning on of thehigh-side NMOS type power transistor of the switching network 102 whenPWM signal at the PWM node 132 is HIGH (e.g., logic 1) and when thevoltage at the SW node 124 equals the voltage at VIN 118.

In FIG. 1 , the example MN2 108 of the example voltage converter 100includes an example MN2 body diode 114 coupled between the MN2 drainterminal and the MN2 source terminal. A body diode is an intrinsicfeature of a MOSFET formed by the PN junction between the drain terminaland a bulk region of a MOSFET, wherein the drain terminal is an n-typematerial and the bulk region is a p-type material for an NMOStransistor. As used herein, the PN junction is a boundary or interfacebetween two types of semi-conductor materials, p-type and n-type,wherein the p-type includes “holes” and is considered positive and then-type includes electrons and is considered negative. In some examples,a body diode is referred to as a parasitic diode, a back-gate diode, oran internal diode.

FIG. 2 illustrates an example schematic of the example switching network102 and an example schematic of the example gate controller 110 thatovercomes the challenge of initiating the three operating states of theexample switching network 102 (e.g., normal mode, one hundred percentmode, and current limit test mode). The illustrated example schematic ofthe gate controller 110 in FIG. 2 includes less power transistorsrelative to other gate controllers and one charge pump (CP), whichdecreases total die area (e.g., block of semiconducting material onwhich a given functional circuit is fabricated) relative to the gatecontrollers that utilize more charge pumps and transistors.

In FIG. 2 , the example schematic of the example switching network 102includes an example third transistor (HSD_BIG) 202, an example fourthtransistor (HSD_SMALL) 204, an example fifth transistor (LSD) 206, anexample pull_down transistor 208, an example inductor (L1) 210, and anexample output capacitor (Cout) 212.

In FIG. 2 , the example schematic of the example switching network 102includes the example HSD_BIG 202 to conduct current from a drainterminal of the HSD_BIG 202 to SW node 124 to charge the example L1 210.The example HSD_BIG 202 includes the drain terminal coupled to the inputvoltage 118, a gate terminal coupled to GATE_BIG node 122, and a sourceterminal of the HSD_BIG 202 coupled to the source terminal of MN2 108, adrain terminal of low-side drive transistor 206, and the example L1 210at the SW node 124. The example HSD_BIG 202 is a high-side drive NMOSwhich conducts large amounts of current (e.g., 1 amp to 8 amps) when ahigh voltage is applied to the gate terminal of HSD_BIG 202 (e.g.,GATE_BIG node 122 is a high voltage). A high-side drive transistor, whenenabled or activated, allows current to flow from supply (e.g., Vin), ora first phase voltage, through an inductor (e.g., L1 210) to an outputcapacitor (e.g., Cout 212), thereby charging the output capacitor Cout212 and increasing the output voltage.

In FIG. 2 , the example schematic of the example switching network 102includes the example HSD_SMALL 204 to conduct current, smaller than thecurrent conducting through the drain terminal of HSD_BIG 202, from adrain terminal of the HSD_SMALL 204 to the SW node 124. The exampleHSD_SMALL 204 includes a drain terminal coupled to the input voltage118, a gate terminal coupled to a drain terminal of an example eleventhtransistor (MP1) 232 of the example gate controller 110; a drainterminal of the example pull down transistor 208; a source terminal ofthe example MP3 214; and the example charge pump 236, and an examplesource terminal coupled to a drain terminal of the example LSD 206 atthe SW node 124 and coupled to an example inductor 210. The exampleHSD_SMALL 204 is the same transistor type as the HSD_BIG 202 except theHSD_SMALL 204 is smaller (e.g., less total channel width) than HSD_BIG202, thereby having a higher impedance (e.g., the HSD_SMALL 204 cannotconduct as much current as HSD_BIG 204). For example, the conductingstate of HSD_SMALL 204 is determined by an example twelfth transistor(MP1) 232 and the MP0 228 of the example gate controller 110, whereinthe MP1 232 is configured to be coupled to the gate terminal of theHSD_BIG 202 and the gate terminal of HSD_SMALL 204 when the voltageconverter 100 is to operate in normal mode or one hundred percent mode,and configured to remove the connection between HSD_BIG 202 andHSD_SMALL 204 when the voltage converter 100 is to operate in currentlimit test mode.

In FIG. 2 , the gate terminal of the example HSD_BIG 202 and the gateterminal HSD_SMALL 204 are coupled together (e.g., when MP0 228 and MP1232 are enabled). For example, the HSD_SMALL 204 replicates theoperation of HSD_BIG 202 (e.g., the HSD_SMALL 204 and HSD_BIG 202operate in parallel). Thus the HSD_SMALL 204 and HSD_BIG 202 conductcurrent from their respective drain terminal that is generated by inputvoltage 118 to L1 210, thereby expanding the L1 210 magnetic field.

In FIG. 2 , the example schematic of the example switching network 102includes the example low-side drive transistor (LSD) 206 to conduct whenthe HSD_BIG 202 and HSD_SMALL 204 are not conducting. The example LSD206 is an N-channel MOSFET that includes a drain terminal coupled to thesource terminal of the example HSD_SMALL 204 at the SW node 124, thesource terminal of HSD_BIG 202, the source terminal of MN2 108, and tothe inductor L1 210. The example LSD 206 also includes a gate terminalcoupled to the example LSD gate driver 105, and a source terminalcoupled to ground. Additionally or alternatively, the example LSD 206may be a P-channel MOSFET, a bipolar junction transistor (BJT), or anyother type of power switching device. A low-side transistor, whenenabled or activated, pulls the SW node 124 to ground, thus creating anegative voltage across inductor L1 210 and thereby decreasing thecurrent (e.g., the magnetic field) flowing through L1 210.

In FIG. 2 , the example schematic of the example switching network 102includes the example pull_down transistor 208 to pull the voltage atGATE_SMALL 240 to ground when the digital signal at an second PWM node133 goes high. For example, when MN2 108 discharges the voltage atGATE_BIG 122 to SW node 124, the pull_down transistor 208 dischargesGATE_SMALL node 240 to ground. The example pull_down transistor 208operates in a saturation mode when the voltage applied to the gateterminal is greater than the Vth of the example pull_down transistor 208and when the voltage at GATE_SMALL node 240 is greater than the Vgsminus Vth. For example, when the pull_down transistor 208 is operatingin saturation mode, the current at GATE_SMALL node 240 conducts to thesource terminal of the pull_down transistor 208 and to ground, resultingin the voltage at GATE_SMALL node 240 to decrease. The example pull_downtransistor 208 operates in cut-off mode when the voltage applied to thegate terminal is less than the Vth. For example, when little to novoltage is applied to the gate terminal of the example pull_downtransistor 208, the voltage at GATE_SMALL node 240 depends on the outputof the example gate controller 110 (e.g., node 126).

In FIG. 2 , the example schematic of the example switching network 102includes the example inductor 210 which is a two terminal electricalcomponent that stores energy in a magnetic field when current flowsthrough it. The example inductor 210 includes a first inductor terminaland a second inductor terminal, the first inductor terminal coupled tothe source terminal of the example HSD_BIG 202, to the source terminalof the example HSD_SMALL 204, the source terminal of the example MN2108, and the drain terminal of the example LSD 206 at the switch node124, and the second inductor terminal coupled to the output capacitorCout 212 at the output node 116. During a high side operation (i.e., theHSD_BIG 202 and/or HSD_SMALL 204 is/are conducting) energy is stored inthe inductor 210. On the other hand, during low side operation (i.e.,the LSD 206 is conducting) energy is discharged from the inductor 210 toground. During low side operation of normal mode, the current flowingthrough the inductor L1 210 is reducing, thereby reducing the energystored in its magnetic field of the example L1 210. The example inductor210 creates a ripple current that occurs during the switching on and offof the HSD_BIG 202 and/or HSD_SMALL 204 and LSD 206. Both HSD_SMALL 204and HSD_BIG 202 are connected to the inductor L1 210. As used herein,ripple current is defined as the peak-to-peak change in current duringthe on time of a switching transistor.

In FIG. 2 , the example schematic of the example switching network 102includes the example output capacitor Cout 212. The example Cout 212 isa two terminal electrical component which stores energy when a voltageis applied across its terminals (e.g., when there is a voltagedifference between the top and bottom plates of the Cout 212). Theexample Cout 212 includes a third capacitor terminal and a fourthcapacitor terminal, the third capacitor terminal is coupled to thesecond inductor terminal of the inductor L1 210.

The example switching network 102 is coupled to the example gatecontroller 110 to facilitate correct current limit operation in normalmode and in one hundred percent mode by shorting GATE_SMALL 240 withGATE_BIG 122 (e.g., via the enabled MP0 228 and MP1 232). The gatecontroller 110 facilitates one hundred percent mode operation byrefreshing the potential at GATE_SMALL 240 and GATE_BIG 122 via thecharge pump 236. Additionally, the gate controller 110 increases thecombined impedance of HSD_BIG 202 and HSD_SMALL 204 in current limittest mode by disconnecting the connection (e.g., creating an opencircuit) between GATE_SMALL 240 with GATE_BIG 122. In this manner, thecharge pump 236 can output a voltage to the GATE_SMALL node 240 to onHSD_SMALL 204 without HSD_BIG 202 turning on also (e.g., while HSD_BIG202 is off) to enable testing of the current limit circuitry with thelimited current capabilities of the ATE resources.

In FIG. 2 , the example schematic of the example gate controller 110which includes an example seventh transistor (MP3) 214, an example eighttransistor 218, an example thirteenth transistor (MN3) 219, an exampleninth transistor (MN1) 222, an example tenth transistor (MP2) 224, anexample eleventh transistor (MP0) 228, an example twelfth transistor(MP1) 232, and an example charge pump (CP) 236.

In FIG. 2 , the example MP3 214, the example eighth transistor 218, theexample MP2 224, the example MP0 228, and the example MP1 232 areP-channel MOSFETS. A P-channel MOSFET is on (e.g., current is conductingout of the drain terminal) when the voltage across the gate terminal andsource terminal is less than a threshold voltage. A P-channel MOSFEToperates in cut-off mode (e.g., current is not conducting from the drainterminal) when the source terminal-to-gate terminal voltage is less thana threshold voltage. Each of the example P-channel; MOSFETS MP3 214,eighth transistor 218, MP2 224, MP0 228, and MP1 232 include an examplebody diode. A body diode is an intrinsic diode formed in the body of atransistor due the PN junction between the p-material and the n-materialof the transistor. For example, a transistor includes a body whichrefers to the bulk of the semiconductor in which the gate terminal,source terminal, and drain terminal are all connected. The body of aP-channel transistor creates an intrinsic body diode due to the PNjunction formed between the n-material of the body and the p-material ofthe source terminal and drain terminal. The example MP3 214 includes adrain terminal coupled to the example eighth transistor 218, a gateterminal coupled to the source terminal of the example MN0 106, and asource terminal coupled to the example GATE_SMALL node 240 at node 126.The example eighth transistor 218 includes a source terminal coupled toan example TEST_GATE node (e.g., test gate node) 246, a gate terminalcoupled to the input voltage 118, and a drain terminal coupled to theexample MP3 214 drain terminal and the MN3 drain terminal of the exampleMN3 transistor 219.

In FIG. 2 , the example MP2 224 includes an example drain terminalcoupled to the input voltage 118, and an example gate terminal coupledto an example source terminal, wherein the source terminal is coupled tothe example MN1 222 at the TEST_GATE node 246. The example MP0 228includes an example drain terminal coupled to the example GATE_BIG node122, an example gate terminal coupled to the TEST-GATE node 246, and anexample source terminal coupled to the example MP1 232. The example MP1232 includes an example source terminal coupled to the MP0 sourceterminal, an example gate terminal coupled to the TEST_GATE node 246,and an example drain terminal coupled to the CP 236 and to the node 126.

In FIG. 2 , the example schematic of the example gate controller 110includes the example MN1 222 to bias the voltage at the TEST_GATE node246 when operating in normal operation to turn on example MP0 228 andexample MP1 232. The example MN1 222 includes an example source terminalcoupled to the input voltage 118, an example gate terminal coupled tothe MP3 gate terminal (e.g., the MP3 gate terminal and the MN1 gateterminal are coupled to the MN0 source terminal and to GATE_BIG node122), and an example drain terminal coupled to TEST_GATE node. In FIG. 2, an electrical effect of a body diode of the example MN2 222 has beenreduced, or otherwise eliminated, by biasing the body of the transistorto ground. For example, MN1 222 does not have the effect of theintrinsic body diode because the intrinsic body diode is alwaysreverse-biased. In this manner, the MN2 222 does not have the sameeffect as the body diodes of example MN2 108, example MP0 228, exampleMP1 232, example MP2 224, and example MP3 214. Body diodes are describedin further detail below in connection with the example fourth body diode220 of FIG. 2 .

In FIG. 2 , the example schematic of the example gate controller 110includes the example charge pump 236 to charge the GATE_SMALL node 240when a voltage is applied to an example enable pin. The example CP 236is a dual purpose CP and is coupled to receive the input voltage 118 andincludes an example output pin coupled the MP1 drain terminal as well asthe GATE_SMALL node at node 126; the source of the example MP3 214; andthe drain of the example pull down transistor 208, and further includesthe example enable pin coupled to an example controller 238. The exampleCP 236 may be a charge-pump doubler. A charge-pump doubler is a chargepump that doubles the amount of input voltage 118 at the output voltageby stacking two capacitors, where one capacitor is coupled to the inputvoltage 118 and ground and the second capacitor is coupled to inputvoltage 118 and the output. Additionally or alternatively, the exampleCP 236 may be an unregulated or pre-regulated doubler, or amulti-capacitor/multi-gain boost CP. The example CP 236 is furtherillustrated in FIG. 7B.

The example schematic of the example gate controller 110 of FIG. 2includes the example controller 238 to enable or disable the example CP236. The example controller 238 may be an oscillator, a PWM generator,etc., which is configured to output some voltage onto TM node 248. Forexample, the controller 238 is configured to generate varying voltagesand currents from a power source to an output (e.g., TM node 248).

The example schematic of the example gate controller 110 of FIG. 2includes the example MN3 219 to provide over voltage protection fortransistor 218 and transistor 214 of the example gate controller 110.The example MN3 219 is an NMOS includes an MN3 gate terminal coupled toan MN3 source terminal and ground. Additionally, the MN3 219 includes anMN3 drain terminal coupled to the drain terminal of the transistor 214and the drain of the transistor 218.

The example voltage converter apparatus 100 includes three operatingmodes, as described above in connection with FIG. 1 . The threeoperating modes are normal mode, one hundred percent mode, and currentlimit test mode. The example switching network 102 and the example gatecontroller 110 operate together in a manner to achieve one of the threedifferent modes of operation of the example voltage converter apparatus100.

In a normal operating mode, the example switching network 102 of FIG. 2provides a regulated output voltage to a load via the output node 116and the example gate controller 110 ensures that GATE_BIG node 122 andGATE_SMALL node 240 are shorted together to ensure that current limitcircuitry operates as intended. The example normal mode operation beginswhen the switchable bias voltage circuit 103 applies a voltage to theMN0 gate terminal based on the PWM signal at the PWM node 132. Forexample, when Vbias is zero volts the voltage at the boot strap node 120is five volts and the switchable bias voltage circuit 103 amplified theincoming PWM signal at the PWM node 132 to ten volts at the MN0 gateterminal, the example MN0 106 turns on and the charge at the boot strapnode 120 flows from the MN0 drain terminal to the MN0 source terminal,which is coupled to the MP3 gate terminal, MN1 gate terminal, MP0 drainterminal, and to the GATE_BIG node 122. The example C_BOOT 112 has notbegun the boot-strapping operation.

Concurrently, the example input voltage 118 is applied to MP2 drainterminal and to the example fourth body diode 226. In normal operationmode, the input voltage 118 forward biases the example fourth body diode226 and charges the TEST_GATE node 246 to the input voltage 118 minusthe voltage drop of the fourth body diode 226. For example, if the inputvoltage 118 is five volts and the body diode 226 is a silicon diode,then five volts minus the voltage drop across the fourth body diode 226is about is 4.3 volts. Thus, the TEST_GATE node 246 is charged to 4.3volts. A silicon diode operating as forward bias has a voltage drop of700 millivolts because of the inherent depletion region of the PNjunction. When the diode is forward biased, the p-type material iscoupled to a positive terminal such as an input voltage 118 and then-type material is coupled to a negative terminal such as a terminal notreceiving voltage. In this manner, when the voltage is applied to thep-type material, the electrons of the n-type material are forced overthe PN junction (e.g., the interface) and some are lost in the process,thus causing the voltage drop across the diode. In other examples, adiode may be less than or greater than 700 millivolts, such as aSchottky diode, a germanium diode, a light emitting diode, etc.

In FIG. 2 , when bootstrapping has not occurred, the example MP3 214,the example MP0 228, and the example MP1 232 are turned off because theMP3 214, MP0 228, and MP1 232 have a Vgs above the threshold voltage.The respective gate-to-source voltages of MP3 214, MP0 228, and MP1 232are above the threshold voltage because during normal operation mode,the example CP 236 is not enabled by the example controller 238. Forexample, the controller 238 outputs zero volts, a logic 0, etc., on theTM node 248 to not enable the CP 236 to double the input voltage 118 atthe output. Further, there is no voltage at node GATE_SMALL node 240because whatever voltage was there has been discharged to ground by theexample pull_down transistor 208.

In FIG. 2 , the example MP0 228 is turned off because the voltage on MP0source terminal and the voltage on TEST_GATE 246 does not meet thethreshold voltage required to turn on the P-channel MOSFET. For example,when the TEST_GATE node 246 has been charged to 4.3 volts, 4.3 volts areapplied to the MP0 gate terminal. In such an example, the MP0 drainterminal is coupled to the MN0 source terminal, which is five volts.Thus, the Vgs of MP0 228 does not meet the Vth to turn on (e.g., 4.3volts-5 volts=−0.7 volts).

In FIG. 2 , when bootstrapping occurs, the example switchable biasvoltage circuit 111 outputs a Vbias and the example C_BOOT 112 booststhe Vbias voltage to a higher voltage at the charge node 120. The secondexample switchable bias voltage circuit 103 outputs a voltage (e.g.,when the signal at the PWM node 132 is high) to the gate of the exampleMN0 106 that is high enough to ensure that the MN0 transistor 106 isturned on. In this manner, the voltage at the MN0 gate terminal isgreater than the voltage at node 120 to turn on the example MN0 106.Further, when the example MN0 106 is turned on, current conducts throughthe MN0 drain terminal to the MN0 source terminal Thus, the voltage atthe MN0 source terminal is the same voltage at GATE_BIG node 122, MP3gate terminal, MN1 gate terminal, and MP0 drain terminal. In response tothe bootstrapping, the example MN1 222, the example MP0 228, and theexample MP1 232 turn on and the example MP3 214 remains turned off. Inthis manner, the example MN1 222 will turn on, and bias the TEST_GATE246 node to the input voltage 118. When the voltage at the TEST_GATEnode 246 equals the input voltage 118, the value of the voltage at theTEST_GATE node 246 is applied to the MP0 gate terminal and the MP1 gateterminal which turns on the example MP0 228 and the example MP1 232. Forexample, the Vgs of both the MP0 228 and the MP1 232 are “negative”because the voltage at the MP0 source terminal and the MP1 drainterminal is greater than the voltage at the MP0 gate terminal and theMP1 gate terminal. The gate-to-source voltages of the MP0 228 and MP1232 are negative because for a PMOS, the voltage at the gate terminalmust be smaller than the voltage at the source terminal to turn on thePMOS (e.g., a differential potential between the gate and the sourcebeing negative turns on the two P-channel MOSFETS MP0 228 and MP1 232.

In this manner, the voltage at GATE_SMALL node 240 equals the voltage atGATE_BIG node 122. For example, the voltage at the MP0 drain terminal isequal to the voltage at the GATE_BIG node 122, and when the example MP0228 turns on, that voltage (e.g., MP0 drain terminal voltage) chargesthe GATE_SMALL node 240 to be equal to the GATE_BIG node 122. Theexample GATE_BIG 202 and the example GATE_SMALL 240 are “shortedtogether” (e.g., the HSD_BIG gate terminal and the HSD_SMALL gateterminal are coupled to each other and receiving identical voltages). Inthis manner, the example voltage converting apparatus 100 is operatingin normal mode because both of the HSD transistors (e.g., HSD_BIG 202and HSD_SMALL 204) are on. Both of the HSD transistors (202 and 204) areturned on and their respective gates have the same potential, thusensuring that the current limiting circuitry is operating as intended innormal mode (GATE_BIG=GATE_SMALL is a hard requirement for the currentlimiting circuitry to operate as intended in normal mode). The SW node124 charges to the input voltage 118 when the example HSD_BIG 202 andthe example HSD_SMALL 204 turn on and there is a positive voltage (e.g.,the voltage at the SW node 124 is greater than the voltage at the output116) across the inductor 210. Thus, the energy is stored in the exampleinductor 210 and the magnetic field of the inductor 210 expands.

In FIG. 2 , the example gate driver 104 may reduce the voltage appliedto the MN0 gate terminal and the MN2 gate terminal to turn off thetransistors MN0 106 and MN2 108. For example, the gate driver 104 may beconfigured to be coupled to receive a control signal from a pulse-widthmodulation (PWM) generator. In some examples, the PWM signal is acontrol signal because it controls the current conducting through thetransistors. The PWM signal is a turn-on and/or turn-off signalgenerated to control the operation of the transistors. A PWM signal isinjected into a gate terminal of a switching transistor via the gatedriver 104. The PWM signal is an oscillating signal varying in dutycycle. Alternatively, the PWM signal may vary in frequency, thereforenoted as a Pulse Frequency Modulated signal (PFM). The PWM and/or PFMsignal injected into the gate terminal via the gate driver 104 containsinformation pertaining to the turn on and/or turn off times of theswitching transistor. For example, the PWM generator may be configuredto provide a plurality of PWM signals to the example MN0 106 (e.g., viathe switchable bias voltage circuit 103), the example MN2 108, and theexample LSD 206, wherein each PWM signal may be the same and turn on thetransistors simultaneously, or they may be different and turn on and offthe transistors in different time intervals.

In FIG. 2 , when the example gate driver 104 removes the voltageinjected into the MN0 gate terminal, it may inject a voltage into theLSD gate terminal. For example, two different PWM signals may be 180degrees out of phase (e.g., include the same frequency but operating inan opposite manner), wherein when the first PWM signal is high, thesecond PWM signal is low, and when the second PWM signal is high, thefirst PWM signal is low. In this manner, the HSD_BIG 202 and HSD_SMALL204 are on when LSD 206 is off, and LSD 206 is turned on when HSD_BIG202 and HSD_SMALL 204 are turned off. This occurs in normal operationmode because the gate driver 104 operates to regulate the voltage at theoutput node 116 by expanding the magnetic field in the example inductor210 when the two high side transistors are turned on and collapsing themagnetic field of the example inductor 210 when the LSD 206 is turnedon, releasing regulated voltage to a load.

In FIG. 2 , the example schematics of the example switching network 102and the example gate controller 110 act to turn on the example HSD_BIG202 before turning on the example HSD_SMALL 204 when operating in normalmode. Turning on the example HSD_BIG 202 first enables the turning on ofthe example MP0 228 and the example MP1 232, which can be referred to asthe switches that connect and/or disconnect the GATE_BIG node 122 andthe GATE_SMALL node 240. During normal operation, when HSD_BIG 202 isturned on first, MP0 228 and MP1 232 automatically turn on. During testmode operation, when the charge pump 236 is turned on first to startcharging the GATE_SMALL, MP0 228 and MP1 232 remain turned offautomatically. Accordingly, the example gate controller 110 is“self-controlled.” Because the structure of MP0 228 and MP1 232 makesthe gate controller 110 self-controlled, the structure of the examplegate controller 110 is simple and consumes little die area.

The second example operating mode is current limit test mode, whereinthe example HSD_SMALL 204 of the example switching network 102 of FIG. 2is permanently on, driven by the example gate controller 110. In thismanner, the gate controller 110 increases the impedance of the switchingnetwork 102 by only turning on the HSD_SMALL 204, which enables thetesting of current limit circuitry, not disclosed herein, with justmilliamps of current (e.g., as opposed to amperes of current), byutilizing hardware such as an ATE system.

The current limit test mode begins when the example controller 238enables the example CP 236. For example, the controller 238 may output alogic 1 or a positive voltage to the enable pin of the CP 236, whichactivates the CP 236 to begin doubling the input voltage 118 at theoutput (e.g., the output of the CP 236 is coupled to node 126 andGATE_SMALL node 240). In some examples, due to inherent capacitances atintermediate node 126 of the example voltage converter apparatus 100,the GATE_SMALL node 240 increases linearly when the CP 236 is activated.As used herein, inherent capacitance is the term used when describingthe unavoidable response of the circuit components in the exampleschematics of the example switching network 102 and the example gatecontroller 110 when there is a change in electric potential (e.g.,voltage).

When the GATE_SMALL node 240 begins to increase due to the charging atthe output of the example CP 236, the voltage at SW node 124 follows thevoltage at GATE_SMALL node 240 because the voltage at SW node 124 isequal to the voltage at GATE_SMALL node 240 minus the Vth of HSD_SMALL204. As the voltage at GATE_SMALL node 240 increases to the inputvoltage 118 plus Vth, the voltage at the SW node 124 reaches the inputvoltage 118 and stays at the input voltage 118 (e.g., the voltage at theSW node 124 cannot surpass this voltage due to the drain terminal ofHSD_SMALL 204 equaling the input voltage 118). The voltage at GATE_SMALLnode 240 continues increasing until the voltage is approximately twotimes the input voltage 118, bringing HSD_SMALL 204 into linear mode(e.g., Vgs−Vth>Vds; as Vgs=Vin and Vds is very small). The voltage dropacross the example HSD_SMALL 204 depends on the current of the drainterminal going into the ON resistance of the transistor (Rdson). Rdsonis a term used to define the resistance of a MOSFET when the MOSFET isoperating in linear mode. The voltage drop across a transistor in linearmode is Rdson times the current at the drain terminal (Id).

In response to the SW node 124 charging and GATE_SMALL node 240charging, the example first body diode 114 coupled to the example MN2108 becomes forward biased, resulting in the current through the forwardbiased diode 114 charging the example GATE_BIG node 122. For example,the voltage at the GATE_BIG node 122 is one diode voltage below thevoltage at the SW node 124, or in other examples, the voltage at theGATE_BIG node 122 is equal to the voltage at the SW node 124 minus thevoltage drop across the example first body diode 114. Additionally, theexample MN2 108 is not turned on because the example gate driver 104 isnot applying a high voltage to the MN2 gate terminal.

When GATE_BIG node 122 is charged to equal one diode voltage below thevoltage at the SW node 124, the example MP3 214 turns on. For example,the MP3 gate terminal is coupled to the GATE_BIG node 122 and the MP3source terminal is coupled to the GATE_SMALL node 240, wherein thevoltage at the MP3 gate terminal is a threshold voltage plus diodevoltage less than the voltage at the MP3 source terminal, causing theMP3 214 to turn on. The voltage at the MP3 source terminal is across theMP3 drain terminal and further forward biases the example third bodydiode 220 that is coupled to the example eighth transistor 218. In thismanner, the example third body diode 220 charges the TEST_GATE node 246to be equal to one diode voltage below the voltage at the GATE_SMALLnode 240. Because, the voltage at the TEST_GATE node 246 is applied tothe MP0 gate terminal and the MP1 gate terminal, the example MP0 228 andthe example MP1 232 are turned off (e.g., because the threshold voltagesof MP0 228 and MP1 232 are greater than one diode voltage, 700millivolts).

In the example current limit test mode, when the example CP 236 chargesthe GATE_SMALL node 240 to be equal to twice the amount of input voltage118, the example HSD_SMALL 204 enters linear mode. During the first halfof the charging phase, HSD_SMALL 204 is in saturation mode (e.g., thevoltage at the SW node 124 is one threshold voltage below the voltage atGATE_SMALL node 240). As the voltage at GATE_SMALL node 240 surpasses atotal voltage equal to the input voltage 118 plus the threshold voltageand the voltage at the SW node 124 reaches the input voltage 118potential, the example HSD_SMALL 204 enters linear mode. In this manner,the voltage at the SW node 124 forward biases the example first bodydiode 114. The example first body diode 114 charges the GATE_BIG node122 to be equal to one diode voltage less than the voltage at the SWnode 124 (e.g., the input voltage 118) because the example HSD_SMALL 204is operating in linear mode and fully on).

The example MP3 214 enters linear mode during the beginning of thecharging phase. The MP3 source terminal is shorted to the MP3 drainterminal and the voltage at the MP3 drain terminal equals the voltage atthe GATE_SMALL node 240. For example, the MP3 source terminal is coupledto the GATE_SMALL node 240 at node 126, and therefore, when the MP3source terminal and MP3 drain terminal are shorted together, the MP3drain terminal receives the voltage at the GATE_SMALL node 240. Further,the gate of the example eighth transistor 218 equals the input voltage118. When the MP3 drain terminal exceeds the input voltage 118 plusthreshold voltage, the eighth transistor 218 turns on (e.g., the eighthtransistor source terminal is one threshold voltage greater than theeighth transistor gate terminal). When the eighth transistor 218 turnson, the voltage at the TEST_GATE node 246 is equal to the voltage at theMP3 drain terminal, and, the voltage at GATE_SMALL node 240. When theTEST_GATE node 246 is charged to equal the voltage at GATE_SMALL node240, the example MP0 228 and the example MP1 232 are in complete cut-offmode, wherein zero current is conducting through the example transistors228, 232. For example, the MP0 drain terminal is coupled to the MP3 gateterminal, which is receiving one diode voltage below the input voltage118, and the MP0 gate terminal is coupled to the TEST_GATE node 246,which is receiving two times the input voltage 118 (e.g., due to the CP236 charging the GATE_SMALL node 240), therefore the MP0 228 is turnedoff.

The example current limit test mode is achieved when the example MP0 228and the example MP1 232 are operating in cut-off mode. For example, whenMP0 228 and MP1 232 are operating in cut-off mode, the HSD_SMALL gateterminal is disconnected from the HSD_BIG gate terminal, and only theHSD_SMALL 204 is turned on. Thus, a higher impedance of the totalhigh-side drive transistor is achieved, since only a portion of thetotal high-side drive transistor (e.g., HSD_SMALL 204) is on. In thismanner, current limit circuitry, not disclosed herein, will trigger at amilliamp level of Isw 244 instead of an ampere level. The increase ofthe impedance (e.g., causing an increase of the voltage drop across theHSD_SMALL 204) aids to test the example current limit circuitry when theATE system is limited to sinking milliamps of current. When the examplecurrent limit test mode is achieved, bootstrapping is not occurring, theexample MN0 106 is not turned on, and the example HSD_BIG 202 is notturned on. The ATE system replaces the inductor L1 210 at the at the SWnode 124 and acts as a current sink (e.g. loads HSD_SMALL 204) duringcurrent limit test mode. Now that the impedance of the parallelcombination of HSD_BIG 202 and HSD_SMALL 204 has increased (e.g., sinceHSD_BIG 202 is off and HSD_SMALL 204 is on), the voltage drop acrossHSD_SMALL 204 and HSD_BIG 202 which is necessary to trigger the currentlimit circuitry will occur at only milliamps of current as compared toamps of current during normal operation, which allows for the currentlimit circuitry to be properly tested by the ATE system.

Internal logic of the gate driver 104 determines when to exit currentlimit test mode by utilizing a second PWM signal at the second PWM node133 to turn on the pull_down transistor 208. For example, when thesecond PWM signal at the second PWM node 133 goes high (e.g., logic 1,threshold voltage, etc.), the pull_down transistor 208 turns on anddischarges the GATE_SMALL node 240 to ground. In this manner, thevoltage at HSD_SMALL gate terminal is removed and HSD_SMALL 204 turnsoff.

Additionally, the example controller 238 assists to exit current limittest mode. The example controller 238 outputs a logic zero to TM node248 to turn off the CP 236, which in turn discontinues charging theintermediate node 126 to only turn on HSD_SMALL 204 and keep HSD_BIG 202off. When the switching network 102 has exited current limit test mode,normal mode or one hundred percent mode can be achieved.

The third example operating mode is one hundred percent mode, whereinthe example high-side drive transistors HSD_BIG 202, HSD_SMALL 204 ofthe example switching network 102 of FIG. 2 are always on. The onehundred percent mode of operation begins in a similar manner as thenormal mode of operation, wherein bootstrapping occurs to turn on theexample HSD_BIG 202 and then turn on HSD_SMALL 204 by activating theexample MP0 228 and the example MP1 232, and the example CP 236 is notenabled. In some examples, the C_BOOT 112 may begin to leak current.Leakage current is a small amount of current that leaks from onecapacitor terminal to the second capacitor terminal, which results in avoltage loss and causes the energy stored in the capacitor to drain. Inone hundred percent mode, leakage current may cause the example HSD_BIG202 and the example HSD_SMALL 204 to turn off if enough charge is lostdue to leakage.

In FIG. 2 , the example CP 236 is enabled during one hundred percentmode to refresh the voltage at the GATE_SMALL node 240 and the voltageat the GATE_BIG node 122. For example, MP0 228 and MP1 232 are turned onand shorted together. In this manner, when the CP 236 is enabled, twotimes the input voltage 118 is injected into the HSD_SMALL gate terminaland two times the input voltage 118 is injected into the HSD_BIG gateterminal, because the two gate terminals are shorted together by MP0 228and MP1 232.

In FIG. 2 , the example CP 236 is dual purpose because it operates toincrease the voltage at GATE_SMALL node 240 in current limit test mode,and it operates to refresh the voltage at GATE_BIG node 122 andGATE_SMALL node 240 in one hundred percent mode. In some examples, thedual purpose CP 236 decreases area size of the example schematic becauseonly one CP is needed and not two to perform the functions describedabove.

While an example manner of implementing the gate controller 110 of FIG.1 is illustrated in FIG. 2 , one or more of the elements, processesand/or devices illustrated in FIG. 2 may be combined, divided,re-arranged, omitted, eliminated and/or implemented in any other way.Further, the example controller 238 of FIG. 2 may be implemented byhardware, software, firmware and/or any combination of hardware,software and/or firmware. Thus, for example, the example controller 238could be implemented by one or more analog or digital circuit(s), logiccircuits, programmable processor(s), programmable controller(s),graphics processing unit(s) (GPU(s)), digital signal processor(s)(DSP(s)), application specific integrated circuit(s) (ASIC(s)),programmable logic device(s) (PLD(s)) and/or field programmable logicdevice(s) (FPLD(s)). When reading any of the apparatus or system claimsof this patent to cover a purely software and/or firmwareimplementation, at least one of the example controller 238 is/are herebyexpressly defined to include a non-transitory computer readable storagedevice or storage disk such as a memory, a digital versatile disk (DVD),a compact disk (CD), a Blu-ray disk, etc. including the software and/orfirmware. Further still, the example gate controller 110 of FIG. 1 mayinclude one or more elements, processes and/or devices in addition to,or instead of, those illustrated in FIG. 2 , and/or may include morethan one of any or all of the illustrated elements, processes anddevices. As used herein, the phrase “in communication,” includingvariations thereof, encompasses direct communication and/or indirectcommunication through one or more intermediary components, and does notrequire direct physical (e.g., wired) communication and/or constantcommunication, but rather additionally includes selective communicationat periodic intervals, scheduled intervals, aperiodic intervals, and/orone-time events.

FIGS. 3 and 4 are example signal plots corresponding to the exampleoperations of the example voltage converter apparatus 100. FIG. 3 is anexample first signal plot 300 corresponding to the current limit testmode operation of the example voltage converter apparatus 100. FIG. 4 isan example second signal plot 400 corresponding to the normal modeoperation of the example voltage converter apparatus 100.

In FIG. 3 , the example first signal plot 300 depicts the voltagethrough the example voltage converter apparatus 100 operating in currentlimit test mode. For example, the first signal plot 300 embodies thevoltage at nodes TEST_GATE 246, GATE_BIG 122, GATE_SMALL 240, and thevoltage at the SW node 124 when the example controller 238 outputs alogic one to the enable pin of the example CP 236 at the TM node 248 andwhen the example gate driver 104 does not output a high voltage at thePWM node 132 signal to the example MN0 106 (e.g., via the exampleswitchable bias voltage circuit 103). In the current limit test mode,the input voltage 118 is 5 volts. However, the input voltage 118 is notlimited to 5 volts.

In FIG. 3 , before time t1, the TEST_GATE node 246 is charged toapproximately 4.8 volts. For example, before the CP 236 is enabled, the5 volt input voltage 118 is dropped across the fourth body diode 226 ofthe MP2 224, wherein the input voltage 118 forward biases the fourthbody diode 226 and charges the TEST_GATE node 246 to equal one diodevoltage below the input voltage 118. In this manner, the example fourthbody diode 226 drops 200 millivolts. At time t1, the example HSD_BIG 202and HSD_SMALL 204 are turned off (e.g., the Vgs_big 202 and Vgs_small204 before time t1 are zero volts and below, indicating that voltage isnot applied to HSD_BIG gate terminal and HSD_SMALL gate terminal).

In FIG. 3 , at time t1, the example controller 238 outputs a logic highto the enable pin of the example CP 236 via TM node 248. In response toenabling the CP 236 at time t1, the voltage at the GATE_SMALL node 240begins to increase. For example, the CP 236 includes an output coupledto the GATE_SMALL node 240 and provides voltage to the GATE_SMALL node240 when enabled. The GATE_SMALL node increases from zero volts to about7 volts at time t1 (e.g., it increases immediately). For example, due toinherent capacitance of the schematic of FIG. 2 , the output of the CP236 does not bring the voltage at node 240 up to two times the inputvoltage 118 immediately.

In FIG. 3 , the example HSD_SMALL 204 begins to turn on as thegate-to-source voltage begins to increase. For example, at time t1, theVgs_small 204 rises from approximately −2 volts to 2 volts when theGATE_SMALL node 240 is being charged by the output of the CP 236. WhenVgs of the example HSD_SMALL 204 increases, the voltage across thetransistor charges the SW node 124. For example, at time t1, the voltageat the SW node 124 rises to the input voltage 118 potential. The voltageat the SW node 124 rises to the input voltage 118 potential because theinput voltage 118 is applied to the HSD_SMALL drain terminal, and whenthe Vgs of HSD_SMALL increases above the threshold voltage, the voltageat the HSD_SMALL drain terminal drops across the transistor to the SWnode 124.

In FIG. 3 , when the voltage at the SW node 124 increases to the inputvoltage 118 potential, the example first body diode 114 becomes forwardbiased and therefore provides voltage to the GATE_BIG node 122 and tothe example MP3 gate terminal. For example, the first signal plot 300illustrates the voltage at GATE_BIG node 122 rising to approximately 4.5volts (e.g., one diode voltage below the voltage at the SW node 124) attime t1. In some examples, the voltage at the GATE_BIG node 122 does notmeet the threshold voltage to turn on HSD_BIG 202, therefore, at timet1, the voltage across the gate-to-source of HSD_BIG 202 begins todecrease because the voltage at SW node 124 has risen due to HSD_SMALL204 turning on.

In FIG. 3 , at time t1, when the example first body diode 114 becomesforward biased, the voltage at the TEST_GATE node 246 begins to increasewith respect to the output of the example CP 236. For example, thevoltage at the MP3 gate terminal is one threshold voltage and one diodevoltage lower than the voltage at MP3 source terminal (e.g., the voltageat the MP3 gate terminal is equal to voltage at GATE_SMALL node 240voltage). Therefore, MP3 214 is in linear mode and the MP3 drainterminal is equal to the voltage at GATE_SMALL node 240. The examplethird body diode 220 is forward biased and voltage at TEST_GATE node 246is one diode voltage below the voltage at GATE_SMALL node 240.

In current limit mode, when the TEST_GATE node 246 is charged to equalthe output of the example CP 236, the Vgs_BIG 202 remains low becausethe MP0 228 and MP1 232 are off. For example, the CP 236 is not chargingGATE_BIG node 122 and thus, HSD_BIG 202 remains off.

In FIG. 3 , at time t2, the voltage at the TEST_GATE node 246 and theGATE_SMALL node 240 have stepped up to equal approximately two times theinput voltage 118 and the Vgs_BIG 202 is still below zero volts,indicating that the example HSD_SMALL 202 is conducting current and theHSD_BIG 202 is turned off. In this manner, the impedance of thehigh-side drive transistor has increased. A voltage difference betweenthe input voltage 118 and the SW node 124 triggers the current limitcircuitry to be tested at milliamps of current (e.g., to be delivered bythe ATE system) as opposed to amps of current during normal operation,thereby enabling ATE testing of the current limit circuitry.

In FIG. 4 , the example second signal plot 400 depicts the voltagethrough the example voltage converter apparatus 100 when operating innormal mode. For example, the second signal plot 400 embodies thevoltage at nodes TEST_GATE 246, GATE_BIG 122, GATE_SMALL 240, and SWnode 124 when the example gate driver 104 receives a high PWM signal atthe PWM node 132. In the normal mode, the input voltage 118 is 5 volts.However, the input voltage 118 may be set to another voltage.

In FIG. 4 , the example second signal plot 400 depicts the PWM signal atthe PWM node 132 going high at time t1. For example, the PWM signal 132rises from zero volts to approximately 2 volts at time t2. The PWMsignal 132 is generated by a PWM generator and is provided to theexample switchable bias voltage circuit 103 to out a voltage sufficientto turn on the example MN0 106. The time between t1 and t2 depicts thepropagation delay of the example gate driver 104. For example, the timebetween t1 and t2 is the time it takes for the example switchable biasvoltage circuit 103 to level shift the PWM signal 132 to a value whichturns on the example MN0 106. When the gate driver 104 receives a highPWM signal 132, it takes time (e.g., 0.00017 microseconds) for theapproximately 2 volt signal to be increased to a value that is largeenough to turn on MN0 106.

In FIG. 4 , the example second signal plot 400 depicts the voltage atGATE_BIG node 122 increasing at time t2. For example, the switchablebias voltage circuit 103 injects an amplified signal into MN0 gateterminal which turns on MN0 106 and further charges the GATE_BIG node122 to equal the voltage at the node 120. When the example GATE_BIG node122 is charged, the Vgs_BIG 202 increases which allows the input voltage118 to discharge through the HSD_BIG drain terminal to the HSD_BIGsource terminal. The voltage at the SW node 124 begins to increase inresponse to the Vgs_BIG 202 increasing as the example HSD_BIG 202 turnson.

Concurrently, the voltage at the TEST_GATE node 246 biases to the inputvoltage 118. For example, when the MN0 106 is turned on, MN1 222 turnson and conducts the input voltage to charge the TEST_GATE node 246. Inthe example second signal plot 400, the TEST_GATE node 246 follows thevoltage at the input voltage 118. The input voltage 118 varies withrespect to inherent capacitances and inductances in the circuitry of theexample voltage converter 100.

In FIG. 4 , the example second signal plot 400 depicts GATE_SMALL node240 increasing at time t2 when the GATE_BIG node 122 increases. Forexample, when the voltage at the GATE_BIG node 122 is increasing, thevoltage is simultaneously applied to the MP0 source terminal and the MN1gate terminal, thus turning on the example MP0 228 and further turningon the example MP1 232. When MP0 228 and MP1 232 are turned on, MP0 228and MP1 232 charge the voltage at node GATE_SMALL 240 to the voltage atnode GATE_BIG 122, creating a short between GATE_BIG 122 and GATE_SMALL240. In response to the voltage at the GATE_SMALL node 240 and GATE_BIGnode 122 charging, the HSD_BIG 202 and HSD_SMALL 204 turn on anddischarge the input voltage to the SW node 124. For example, the voltageat the SW node 124 begins to increase at time t2 with respect to thevoltage at GATE_BIG node 122 and GATE_SMALL node 240 increasing.

In FIG. 4 , the example second signal plot 400 depicts the voltageacross Vgs_BIG 202 and Vgs_SMALL 204 increasing to a maximum potentialat time t3. For example, at time t3, the voltage at each node 122 and240 have increased to equal the voltage provided by the Cboot 112, andthe voltage provided by Cboot 112 fully turns on the example HSD_BIG 202and HSD_SMALL 204 as indicated by the gate-to-source voltage (Vgs)signals. At time t3, the charging of all nodes (e.g., GATE_BIG node 122and GATE_SMALL node 240) is complete.

Turning to FIG. 5 , a test mode implementation 502 and the example gatecontroller 110 are depicted in a silicon diagram to display thedifference in total area size between the test mode implementation 502and the example gate controller 110. For example, the test modeimplementation 502 includes a test mode switch and a charge pump andoperates to perform similar functions as that of the example gatecontroller 110. The test mode implementation 502 is greater in physicalsize than the example gate controller 110, even though they perform thesame functions. For example, the test mode implementation 502 isapproximately 11,670 square micrometers and the example gate controller110 is approximately 2,310 square micrometers.

FIG. 5 illustrates an improvement of the example gate controller 110over the test mode implementation 502 by minimizing the area size andnumber of components required to perform the functions of normal mode,one hundred percent mode, and current limit test mode. The reduction indie area consumption is due to a single charge pump (e.g., the chargepump 236) and minimizes production costs. The example gate controller110 is able to connect and/or disconnect GATE_BIG and GATE_SMALL withless components and more simplicity than the example test modeimplementation 502 (e.g., because MP0 228 and MP1 232 areself-controlled and do not require special level shifting). Accordingly,the example gate controller 110 is implemented in a smaller die areathan the example test mode implementation 502. For example, thereduction in total number of components reduces the complexity of thegate controller 110 and likelihood that errors occur during building andoperation. Thus, the decrease in the number of components and die arearesults in a decreased cost of implementing a circuit for normal, onehundred percent, and/or current limit test mode. The example gatecontroller 110 is approximately 9,360 square micrometers smaller thanthe test mode implementation 502. By including less components and beingsmaller in physical size, the example gate controller 110 generates lesselectromagnetic interference (EMI), dissipates less heat, includes afaster response time, and is cost efficient. In other examples, the gatecontroller 110 is cost efficient because there are fewer componentsrequired, such as one dual purpose charge pump (e.g., in the gatecontroller 110) versus two charge pumps (e.g., in the test modeimplementation 502).

FIG. 6 illustrates a system layout 600 of the gate driver 104 whichincludes additional components and devices relative to the schematicillustrated in FIG. 2 . The outlined gate controller 110 of the systemlayout 600 is depicted as a small portion of the high-side drive gatedriver 104 which controls three modes of operation of the HSD transistor(e.g., HSD_BIG 202 and HSD_SMALL 204) of the switching network 102. Thesystem layout 600 utilizes the plurality of electrical components toadjust the voltages provided to the HSD transistor of the switchingnetwork 102. The system layout 600 may be implemented as a separatemodule than the switching network 102 or may be implemented on the sameIC as the switching network 102.

A flowchart representative of example hardware logic, machine readableinstructions, hardware implemented state machines, and/or anycombination thereof for implementing the voltage converter apparatus 100of FIG. 2 is shown in FIG. 7 . The machine readable instructions may beone or more executable programs or portion(s) of an executable programfor execution by a computer processor. The program may be embodied insoftware stored on a non-transitory computer readable storage mediumsuch as a CD-ROM, a floppy disk, a hard drive, a DVD, a Blu-ray disk, ora memory associated with the processor, but the entire program and/orparts thereof could alternatively be executed by a device other than theprocessor and/or embodied in firmware or dedicated hardware. Further,although the example program is described with reference to theflowchart illustrated in FIG. 7 , many other methods of implementing theexample voltage converting apparatus 100 may alternatively be used. Forexample, the order of execution of the blocks may be changed, and/orsome of the blocks described may be changed, eliminated, or combined.Additionally or alternatively, any or all of the blocks may beimplemented by one or more hardware circuits (e.g., discrete and/orintegrated analog and/or digital circuitry, an FPGA, an ASIC, acomparator, an operational-amplifier (op-amp), a logic circuit, etc.)structured to perform the corresponding operation without executingsoftware or firmware.

The machine readable instructions described herein may be stored in oneor more of a compressed format, an encrypted format, a fragmentedformat, a packaged format, etc. Machine readable instructions asdescribed herein may be stored as data (e.g., portions of instructions,code, representations of code, etc.) that may be utilized to create,manufacture, and/or produce machine executable instructions. Forexample, the machine readable instructions may be fragmented and storedon one or more storage devices and/or computing devices (e.g., servers).The machine readable instructions may require one or more ofinstallation, modification, adaptation, updating, combining,supplementing, configuring, decryption, decompression, unpacking,distribution, reassignment, etc. in order to make them directly readableand/or executable by a computing device and/or other machine. Forexample, the machine readable instructions may be stored in multipleparts, which are individually compressed, encrypted, and stored onseparate computing devices, wherein the parts when decrypted,decompressed, and combined form a set of executable instructions thatimplement a program such as that described herein. In another example,the machine readable instructions may be stored in a state in which theymay be read by a computer, but require addition of a library (e.g., adynamic link library (DLL)), a software development kit (SDK), anapplication programming interface (API), etc. in order to execute theinstructions on a particular computing device or other device. Inanother example, the machine readable instructions may need to beconfigured (e.g., settings stored, data input, network addressesrecorded, etc.) before the machine readable instructions and/or thecorresponding program(s) can be executed in whole or in part. Thus, thedisclosed machine readable instructions and/or corresponding program(s)are intended to encompass such machine readable instructions and/orprogram(s) regardless of the particular format or state of the machinereadable instructions and/or program(s) when stored or otherwise at restor in transit.

As mentioned above, the example processes of FIG. 7 may be implementedusing executable instructions (e.g., computer and/or machine readableinstructions) stored on a non-transitory computer and/or machinereadable medium such as a hard disk drive, a flash memory, a read-onlymemory, a compact disk, a digital versatile disk, a cache, arandom-access memory and/or any other storage device or storage disk inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, for brief instances, for temporarily buffering,and/or for caching of the information). As used herein, the termnon-transitory computer readable medium is expressly defined to includeany type of computer readable storage device and/or storage disk and toexclude propagating signals and to exclude transmission media.

“Including” and “comprising” (and all forms and tenses thereof) are usedherein to be open ended terms. Thus, whenever a claim employs any formof “include” or “comprise” (e.g., comprises, includes, comprising,including, having, etc.) as a preamble or within a claim recitation ofany kind, it is to be understood that additional elements, terms, etc.may be present without falling outside the scope of the correspondingclaim or recitation. As used herein, when the phrase “at least” is usedas the transition term in, for example, a preamble of a claim, it isopen-ended in the same manner as the term “comprising” and “including”are open ended. The term “and/or” when used, for example, in a form suchas A, B, and/or C refers to any combination or subset of A, B, C such as(1) A alone, (2) B alone, (3) C alone, (4) A with B, (5) A with C, (6) Bwith C, and (7) A with B and with C. As used herein in the context ofdescribing structures, components, items, objects and/or things, thephrase “at least one of A and B” is intended to refer to implementationsincluding any of (1) at least one A, (2) at least one B, and (3) atleast one A and at least one B. Similarly, as used herein in the contextof describing structures, components, items, objects and/or things, thephrase “at least one of A or B” is intended to refer to implementationsincluding any of (1) at least one A, (2) at least one B, and (3) atleast one A and at least one B. As used herein in the context ofdescribing the performance or execution of processes, instructions,actions, activities and/or steps, the phrase “at least one of A and B”is intended to refer to implementations including any of (1) at leastone A, (2) at least one B, and (3) at least one A and at least one B.Similarly, as used herein in the context of describing the performanceor execution of processes, instructions, actions, activities and/orsteps, the phrase “at least one of A or B” is intended to refer toimplementations including any of (1) at least one A, (2) at least one B,and (3) at least one A and at least one B.

Turning to FIG. 7 , the program 700 depicts an operation of the examplegate controller 110 of FIG. 2 to operate in current limit test mode andone hundred percent mode. The program 700 of FIG. 7 begins at block 702where the gate driver 104 determines the incoming PWM signal value atthe at the PWM node 132. For example, the gate driver 104 receives asignal from a controller, oscillator, signal generator, etc., which is alow-voltage signal (LOW) or a high-voltage signal (HIGH).

When the PWM signal at the PWM node 132 is HIGH (e.g., block 702 returnsa YES), the MN2 108 and the pull_down transistor 208 are turned off(block 704). For example, when the PWM signal at the PWM node 132 isHIGH, the second PWM signal at the second PWM node 133 goes LOW, suchthat the low-voltage signal turns off the MN2 108 and the pull_downtransistor 208. Additionally, in response to the HIGH PWM signal at thePWM node 132, the MN0 106 turns on (e.g., the switchable bias voltagecircuit 103 outputs a voltage sufficient to turn on the MN0 106 with thePWM signal is HIGH) (block 706).

The HIGH PWM signal at the PWM node 132 is also applied to theswitchable bias voltage (SBV) circuit 111. The switchable bias voltagecircuit 111 outputs switchable bias voltage to charge bootstrap node 120(e.g., via the C_BOOT 112) (block 708). For example, a controller (e.g.,a PWM generator) provides a high voltage signal to the gate driver 104which initiates the switchable bias voltage circuit 111 to provide thebias voltage to the Cboot 112. When the bootstrap node 120 is charged(block 708), the MN0 106 charges GATE_BIG node 122 to go high (block710). For example, the MN0 106 is turned on causing the voltage at theGATE_BIG node 122 to be equal to or substantially similar to the voltageat the bootstrap node 120.

Additionally, MP0 228 and MP1 232 turn on (block 712) in response tobootstrap node 120 charging. When MP0 228 and MP1 232 turn on,GATE_SMALL node 240 is pulled HIGH (e.g., the voltage at GATE_SMALL node240 increases). For example, MP1 drain terminal is coupled to GATE_SMALLnode 240 and charges GATE_SMALL node 240 when MP1 232 is turned on. Inresponse to the MP0 228 and the MP1 232 turning on, GATE_BIG node 122and GATE_SMALL node 240 are shorted together (block 714).

When the GATE_BIG node 122 and GATE_SMALL node 240 are shorted (block714), HSD_BIG 202 and HSD_SMALL 204 are fully on (block 716). Forexample, the voltage applied to the GATE_BIG node 122 turns on HSD_BIG202 and the voltage applied to the GATE_SMALL node 240 turns onHSD_SMALL 204. In this manner, GATE_BIG 122 is equal to GATE_SMALL 240.

When HSD_BIG 202 and HSD_SMALL 204 are both fully on (block 716), thereis a low impedance connection between Vin 118 and SW node 124 (block718). During operation (e.g., HSD_BIG 202 and HSD_SMALL 204 are turnedon), the C_BOOT 112 may begin to leak current. In this manner, the CP236 is turned on (block 720), and, because GATE_BIG 122 and GATE_SMALL240 are shorted together by MP0 228 and MP1 232, the CP 236 replenishesthe lost charge on both GATE_BIG 122 and GATE_SMALL 240 (block 714).

The CP 236 continues to refresh the voltage at GATE_BIG node 122 andGATE_SMALL node 240 when PWM signal at the PWM node 132 is HIGH (e.g.,block 722 returns a YES). When the PWM signal at the PWM node 132 goesLOW (e.g., block 722 returns a NO), the MN2 108 and pull_down transistor208 are turned on and the CP 236 and MN0 106 are turned off. Forexample, the second PWM signal at the second PWM node 133 goes HIGH andprovides a turn-on voltage (e.g., a voltage value above Vth) to the MN2gate terminal and the pull_down transistor gate terminal.

When MN2 108 and pull_down transistor 208 are turned on, the HSD_BIG 202and the HSD_SMALL 204 turn off (block 726). For example, when thepull_down transistor 208 is turned on, the voltage at GATE_SMALL node240 shorts to ground, thus removing the voltage from HSD_SMALL gateterminal and turning off HSD_SMALL 204. Additionally, when the MN2 108is turned on, it discharges the GATE_BIG node 246 to the SW node 124. Inthis manner, the GATE_BIG node 122 shorts to SW node 124, therebyreducing the gate voltage of the HSD_BIG 202 and HSD_BIG 202 is turnedoff. When MN2 108 is turned on, the voltage at MP0 drain terminal isreduced to 0 volts, thus turning off MP0 228 and MP1 232.

If the gate driver 104 receives a signal from a controller, oscillator,signal generator, etc., which is a LOW (e.g., block 702 returns a NO)then the program 700 of FIG. 7 begins at block 730, where current limittest mode is determined to be activated. For example, when PWM signal atthe PWM node 132 is LOW, the controller 238 (FIG. 2 ) may receive aninitiating signal indicative to activate current limit test mode (e.g.,block 730 returns a YES). In other examples, when PWM signal at the PWMnode 132 is LOW, the controller 238 may not receive an initiating signalindicative to activate current limit test mode (e.g., block 730 returnsa NO). In this manner, the example gate controller 110 continues to waitfor a HIGH or LOW PWM signal at the PWM node 132 (block 702).

When current limit test mode is determined to be activated (e.g., block730 returns a YES), a controller, such as a PWM generator, oscillator,signal generator, etc., turns off the example MN2 108 and pull_downtransistor 208 (block 732). For example, the PWM signal 133 goes low andreduces the gate voltage of the MN2 gate terminal and pull_downtransistor gate terminal to 0 volts, thereby turning off the MN2 108 andthe pull_down transistor 208.

When the MN2 108 and pull_down transistor 208 are turned off (block732), the controller 238 turns on CP 236 (block 734). For example, thecontroller 238 outputs a high voltage signal (e.g., greater than zerovolts) to the enable input of the example charge pump 236 via the TMnode 248. The output of the CP 236 charges the GATE_SMALL node 240. Forexample, when the charge pump 236 is enabled, the charge pump 236operates to double the input voltage 118 at the output (e.g., theintermediate node 126).

When the CP 236 is charging, the voltage at the GATE_SMALL node 240, theMP0 228 and MP1 232 remain off (block 736). For example, MP0 228 and MP1232 are, by default, turned off. Because the output of the CP 236 iscoupled to the source terminal of MP3 214, the potential at the sourceterminal of MP3 214 becomes higher than the potential at the gateterminal of the MP3 214, thereby turning the MP3 214 on. Thus, the drainterminal of the MP3 214 receives the voltage at the GATE_SMALL node 240and passes the voltage to the drain terminal of the eighth transistor218. Once the voltage at the GATE_SMALL node 240 surpasses Vin plus thethreshold voltage of the eighth transistor 218, the eighth transistor218 turns on and passes the voltage at the GATE_SMALL node 240 to theTEST_GATE node 246 (e.g., the gates of the MP0 228 and the MP1 232).Thus the voltage at the GATE_SMALL node 240 is applied to the gate ofMP1 232 and to the source of MP1 232. Because the Vgs of MP1 232 is zerovolts, the MP1 232 is off. When MP0 228 and MP1 232 are both off, thereis an open between GATE_SMALL node 240 and GATE_BIG node 122 (block738). For example, MP0 228 and MP1 232 are the transistors thatinherently act as the switch between the gate terminals of HSD_BIG 202and HSD_SMALL 204 (e.g., the GATE_BIG node 122 and GATE_SMALL node 240),thus shorting or opening the connection between the two HSD transistors202, 204.

When the CP 236 is charging GATE_SMALL node 240, creating an openbetween GATE_BIG node 122 and GATE_SMALL node 240, the HSD_SMALL 204turns fully on and the HSD_BIG 202 is off (block 740). For example,there is no voltage charging GATE_BIG node 122, thus the voltage atHSD_BIG gate terminal is not great enough to turn the HSD_BIG 202 on.Because the output of the CP 236 is coupled to the source terminal ofMP3 214, the potential at the source terminal of MP3 214 becomes higherthan the potential at the gate terminal of the MP3 214, thereby turningthe MP3 214 on. Thus, the drain terminal of the MP3 214 receives thevoltage at the GATE_SMALL node 240 and passes the voltage to the drainterminal of the eighth transistor 218. Once the voltage at theGATE_SMALL node 240 surpasses Vin plus the threshold voltage of theeighth transistor 218, the eighth transistor 218 turns on and passes thevoltage at the GATE_SMALL node 240 to the TEST_GATE node 246 (e.g., thegates of the MP0 228 and the MP1 232). Thus the voltage at theGATE_SMALL node 240 is applied to the gate of MP1 232 and to the sourceof MP1 232. Because the Vgs of MP1 232 is zero volts, the MP1 232 isoff.

The example gate controller 110 operates to keep the HSD_BIG 202 off incurrent limit test mode because when HSD_BIG 202 is off, the impedanceof the switching network 102 increases and the ATE hardware has theability to test current limit circuitry without additional resources.For example, there is a high impedance connection between Vin 118 and SWnode 124 (block 742). The high impedance connection is a result of theHSD_BIG 202 being turned off. Thus, HSD_BIG 202 acts as an open circuitbetween Vin 118 and SW node 124. Because HSD_SMALL 204 is on (e.g.,creating a short circuit between Vin 118 and SW node 124), current willflow though HSD_SMALL 204 (as opposed to both HSD_SMALL 204 and HSD_BIG202), thereby increasing the impedance between Vin 118 and the SW node124. Additionally, HSD_SMALL 204 is a smaller transistor (e.g., smallerin physical size relative to the HSD_BIG 202) and a voltage differencebetween Vin 118 and SW node 124 which is sufficient to trigger thecurrent limiting circuitry already occurs at milliamps of current (e.g.,as opposed to amps of current when HSD_BIG 202 is turned on also). Inthis manner, current limiting circuitry can be tested with milliamps ofcurrent offered by ATE hardware.

The gate driver 104 may continue receiving an initiating signalindicative to active current limit test mode (e.g., block 744 returns aresult YES) when operating in current limit test mode. If the gatedriver 104 receives a signal indicative of inactive current limit testmode, the current limit test mode is to be no longer activated (e.g.,block 744 returns a NO). In this manner, MN2 108 and the pull_downtransistor 208 are turned on and the CP 236 is turned off (block 746) toremove the gate voltage from MP3 214 and HSD_SMALL 204, thus turning offMP3 214 and HSD_SMALL 204 (block 748).

The program 700 ends when the HSD_BIG 202 and HSD_SMALL 204 are bothoff. The program 700 may be repeated when the gate driver 104 receives aHIGH PWM signal at the PWM node 132 or when the gate controller 110receives a signal indicative of instructions to activate current limittest mode of the gate driver 104.

From the foregoing, it will be appreciated that example methods,apparatus and articles of manufacture have been disclosed that reducethe number of components used to implement three modes of operation:normal mode, one hundred percent mode, and current limit test mode, fora switching network. The disclosed methods, apparatus and articles ofmanufacture increase the versatility of a switching network byimplementing circuitry to perform multiple operations without requiringthe need for a plurality of circuits to perform the multiple operations.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. An apparatus comprising: a switching network thatincludes a first high-side drive (HSD) transistor having a first HSDgate and a second HSD transistor having a second HSD gate, wherein theswitching network has a current limit test mode, a normal mode and a onehundred percent mode; and a gate controller having first and secondswitches and a third transistor, wherein the third transistor is coupledbetween the second HSD transistor and the second switch, the first andsecond switches are configured to connect the first HSD gate to thesecond HSD gate during at least one of the normal mode or the onehundred percent mode, and the gate controller is configured to turn onthe second HSD transistor while the first HSD transistor is off duringthe current limit test mode.
 2. The apparatus of claim 1, wherein thegate controller is configured to refresh a voltage applied to a gateterminal of the first HSD transistor responsive to the switching networkoperating in the one hundred percent mode.
 3. The apparatus of claim 1,wherein the first HSD gate is disconnected from the second HSD gateresponsive to the switching network being in the current limit testmode.
 4. A system comprising: a first transistor having first and secondcurrent terminals and a first control terminal; a second transistorhaving third and fourth current terminals and a second control terminal,wherein the second control terminal is coupled to the first controlterminal, and the third current terminal is coupled to the secondcurrent terminal; a charge pump coupled between an input terminal andthe fourth current terminal; and a switching network coupled to thefourth current terminal, wherein the switching network includes a firsthigh-side drive (HSD) transistor and a second HSD transistor, and theswitching network has at least three modes of operation that include acurrent limit test mode.
 5. The system of claim 4, wherein the at leastthree modes include a normal mode and a one hundred percent mode.
 6. Thesystem of claim 5, wherein the charge pump is configured to refresh avoltage applied to a gate terminal of the first HSD transistor while theswitching network is operating in the one hundred percent mode.
 7. Thesystem of claim 4, wherein the first and second transistors arep-channel transistors.
 8. The system of claim 4, further comprising agate driver coupled to the switching network.